Methods for forming a structural body including a brittle material on the surface of a base material include e.g. the aerosol deposition method and the gas deposition method (International Patent Publication WO 01/27348, Japanese Unexamined Patent Publication No. 2007-162077, Japanese Unexamined Patent Publication No. 2005-2461). In the aerosol deposition method and the gas deposition method, fine particles including a brittle material is dispersed in a gas to form an aerosol. The aerosol is squirted from a jetting port toward the base material. Thus, the fine particles are caused to impinge on the base material such as metal, glass, ceramic, and plastic. The brittle material fine particles are deformed or fractured by the impact of this impingement, and joined. Thus, a film-like structural body including the constituent material of the fine particles is directly formed on the base material.
This method can form a film-like structural body at normal temperature without particularly requiring heating means and the like. This method can obtain a film-like structural body having a mechanical strength comparable or superior to a fired body. Furthermore, the density, mechanical strength, electrical characteristic and the like of the structural body can be variously changed by controlling e.g. the condition of impingement of fine particles, and the shape and composition of fine particles.
However, this method applies impact by repetitive impingement of fine particles to form a compact structural body. Thus, stress remains in the film-like structural body and the base material at the time of film formation. For instance, a relatively large stress is locally applied near the boundary of the film formation region and the protruding part of the base material. The problem is that in the portion subjected to a relatively large stress, the film-like structural body may be peeled by self-collapse of the film-like structural body.
Furthermore, for instance, in the case of forming a film-like structural body on a flat surface or side surface, a relatively large stress is locally applied near the boundary of the film formation region. Starting from this boundary, the film-like structural body may be peeled. Moreover, in the case where the end part of the film-like structural body is provided in the surface of the target (base material) of the formation of the film-like structural body, stress concentrates near the end part. Thus, thickening of the film thickness may cause self-collapse of the film-like structural body. Peeling and self-collapse of the film-like structural body may occur not only immediately after the formation of the film-like structural body, but also after the lapse of e.g. one day or one week, because of fatigue due to stress accumulated in the film-like structural body or the base material.